Inductive wireless-telephone system for railroads and the like.



v T. e THI J RNB LAD, K. H. WARFVINGE & v. s. WERNER.

INDUCTIVE WIRELESS TELEPHONE SYSTEM FOR RAILROADS AND THE LIKE.

APPLICATION FILED JUNE 5| 1914.

lnvon for:

Patented Feb. 20.1917;

UNITED STATES PATENT OFFICE.

THOR GUSTAF THfiRNBLAD, KARL HJALMAR WAR-FVINGE, AND VICTOR GABRIEL WERNER, 0F STOOKHOLM, SWEDEN.

INDUCTIVE WIRELESS TELEPHONE SYSTEM FOR RAILROADS AND THE LIKE.

7b all-whom it may concern:

Be it known that we, THOR Gosrar Tl1iiBNBLAD,I{ARL HJALMAR W nrvrNon, and

VICTOR GABRIEL VVnnNnn, subjects of the tages so great, thatit must be supposed from the mere description of the same, that said system has never been put to practical tests, nor could it be mentioned a solution of the problem of communication ment is the following, based on the principle of induction from one coil to another. On a railroad car-or it may, generally speaking, be a vehiclethe1 -e is placed a coil of comparatively small size. Connected to said coil is an ordinary microphone and a source jmicrophone and a convenient source of electrical supply, when speaking to the vehicle,

and a receiver when hearing. Thus, electrically, the system described consists in the induction from a smaller coil to a greater,

and vice versa.

It is stated as an essential part of this system, that the greater coil consists. of a plurality'of convolutions, and it is obvious that this, system will result in no telephonic-comlnunication, if the greater coil does not consist of a plurality of convolutions. Itis evident, however, that such ing is to take place, is connected with greatarrangement as that described, comprlsing a great coil with manv 'con'voluti'ons sur roundingthe whole field. in which telephon disadvantages. Thus, a, system of such a kind must result in immense costs of erect Specification of Letters Patent.

Application filed June 6, 1914.

between trains and stations; I In short, the arrange- Patented Feb. 20, 1917.

Serial no. 843,362.

ing and maintaining, on account of the mentioned coil around the path of travel.

Being aware of this disadvantage we have devoted our efforts to invent such a system that the use of a stationary coil is entirely eliminated.

After elabo 'ate experiments we have finally invented a system, whereby instead of the mentioned troublesome and costly coil-building we make use of the ordinary telephone or telegraph wires running along the railroad or we may use an especially erected single-wire line. An essential feature of our system in contradistinction to that described is, that we may. use a singlewire line, when in the other system no results can be obtained without an impractical coilbu'ilding. However, no communication can be established by. means'of such a singlewire line with the use of an ordinary micro phone, as in the system referred. to. It is essential and necessary here. to inake'use of a microphone belonging to another class viz. a so called strong-current microphone. Microphones belonging to the so called strong-current microphone class differ from ordinary microphones inthis essential feia ture, that microphones of the first-named kind, due to characteristic arrangements,

permita considerably greater direct current.

energy to be transferred into alternating current energy than is possible with the ordinary microphone. All the. characteristic arrangements in stron -current micro )hones, referred to above an making possi le the use of considerably stronger sources of electrical energy, have" for aim, whatever they may be, to enable the strong-current microhone to withstand the influence ofthe heatmg efiect of the electrical current upon the .This wire is grounded at both ends, butin some instances'it may be preferable to providethe same with a returningf -part. i. a wire or conductor betw-l u the points Band.

3. To this wire 1 is connected :1 le]cplione receiver' l at a station on the raih oad, I On a car of the train there 1s located a circuit,

Fig. 2 illustrates an arrangement whereby I it' is possible to transmit speech from the railroad station to a moving train. The wire 8 along the railway track is preferably grounded at both ends and at one end, suit ably at the railroad station,there is connected to the Wire 8 a, strong-current microphone 9 and a powerful battery 10. On a car of, the train is located an induction frame 1-1, to which a receiver 12 is connected in series. 5 duced in the wire 8 when speaking into the microphone 9' will produce corresponding alternating currents in the induction frame 11 on the train, which will cause the speech I to be heard in the receiver 12.

i 3 By combining the arrangement shown in V Fig. 1 for transmitting speech from the train to the station and that shown in Fig. 2

'for transmitting speech from the station to the train, the arrangement illustrated in 5 Fig, 3 may be obtained, by means of which it is possible to talk from the train to the station and vice versa. At the station at one end of the wire 13 the switch 14 is connected to the same by meansof which either the receiver 15 or thestrong-current microphone 16 and the battery 17 'may be connected in series with the wire 13. On a car of the train is located an induction frame 18, to the circuit of which. by means of a switch 19 may be connected either a receiver 2Q or astrong-current microphone 21 and a powerful battery '22. In theshown positions of the switches 14 and 19 these are set for speech to be transmitted from the train to the station. When it is desired to talk from the station to the train the switches 14 and 19 are moved over to their positions shown in dotted line .'when the microphone 1'6 and the batter 17 will be 5 .connected with the wire 13, and the receiver 20 will be connected to th induction frame 18..

In Fig. 4 we have illustrated another arrangement for speaking from he train to the station and vice v'ersa. Th apparatus at the station is connected in tl'lt same man'- ner as shown in Fig. 3 and comprise a switch 23, a stroIig-current microphone 2d, a powerful battery 25, and a receiver 26.

6 On a. car of the train there are arranged two The pulsating currents pr the drawing induction frames 27 and 28, of which the frame 27 is connected to the strong-current microphone 29'and powerful battery 30, the other frame 28 bein connected in series with a receiver 31. T

ranged in the longitudinal direction of the car, 2'. 6. so that their long sides will be approximately parallel to the wire 32 running along the railroad track, and so that their short sides are abutting. By this arrangement the advantage is attained that it is possible to speak from the train and at the same time to hear the speech in the receiver 31, without having to operate a switch.- f Fig. 5 illustrates an arrangement whereby two wires and 34 ordinarilyused for telephoning between two stations and 36 on the railroad, may be used for transmitting speech from a train to other stations. The induction frame and the apparatus on the train are indicated by 37 and 38 respectively. 39 and 40 represent two stations provided with apparatus as shown in Figs B and 4. These stations are connected to the'wires 33 and 34 by a duplex connection familiar to those skilled in the art, and we do not deem it necessary to further describe the same. By means of switches 41 and42 these stations 39 and. 40 may be connected to or disconnected from the wires 33 and 34, ground connections 43 and 44 being provided for grounding that end of the line where the apparatus at the station isnot connected to the wires. Itis :obvious that telephoning may take placefrom the train over the wires 33 and 34 to any of the stations 39 and-40 without disturbing the transmitting of messages from one of the stations 35 and 36 to the other.

In Fig. 6 we have shown a suitable way of connecting a wire along the railroad track to several stations in such manner that the wire will be divided in sections, in order to make the circuits foreach station as short as possible. A, B, O and I) represent four stations on the railroad, thestations A and B being each provided with one of our telephone apparatus 45 and 16, and the stations O and D each with two 47, 43, it) and 50. The wire 51 along the railroad tra k is, as

shown in the drawing, divided in sections' between the stations, theends of each section being connected to the apparatus at the station either by means of switches 52 and 53, as shown at the stations A and B, or directly as at the stations 0 and D. At points intermediate the stations the wire 51 is grounded. 54, 55 and 56-:"iive'present trains moving onthe railroad. It is e t from that'in the shown tfihbitions of the switches 52 and 53, thes t'ation ,A is in communication with the 'fiifziin 54 and the station B with the train 5,5, The train 56 is in communication the apparatus 49 he frames 27 and. 28 'are preferably of oblong shape and ar- 1,21e,ss7

at station D.- When all trains have moved into the right hand halves of the sections the train 54' will be in communication for railroads, the

.with the station B,'after' the switch 53 has beenm'oved over to the dotted position, the train 55. will be in communication with the apparatus at the stationC, and the train 56 with the apparatus50 at the station D.

We claix'n: y

- In an inductive wireless telephone system combination of a circuit on the train comprising a strong-current microphone,

trical energy, and a stationary circuit a recelver, and a source of elec formed by telegraph or tele hone wires along-the railroad track used For the ordinary telegraph and telephone traflic and comprising a strong-current microphone, a receiver, said circuits being -poee set forth.

THOR GUSTAF THORNBLAn. KARL HJALMAR WARFVINGE. VICTOR GABRIEL WERNER. r I I Witnesses: l Fnnnmm Sonm'rrsmiiwi Tmnm Osmnmxwe. V

and a source of electrical energy,

1n inductive relation to each other, substantially as and for the pur- 

